It is well known in the art of climate controls for automotive vehicles to provide reciprocating piston compressors for pressurizing a refrigerant such as freon gas. It is also known practice to use a scroll type compressor, which tends to reduce vibrations caused by reciprocating pistons and to provide higher volumetric and mechanical efficiency. The dynamic behavior of such conventional compressors is described in the literature; e.g., a paper entitled A Study On Dynamic Behavior Of A Scroll Compressor, published in the 1986 International Compressor Engineering Conference at Purdue University, Vol. 3, Aug. 4-7, 1986. The authors are Ishii, Fukushima, Sano and Sawai.
With the introduction of an alternate refrigerant commonly known as "R134A", which may replace freon gas as a refrigerant in automotive vehicle air conditioning systems, it is necessary to provide higher operating pressures. This tends to introduce problems associated with sealing the refrigerant. The use of this alternate refrigerant also makes it necessary to provide a higher volumetric efficiency than the efficiencies associated with compressors used with Freon gas and to deal with higher temperature of the inlet gas.
An example of a compressor that is adapted especially for use with "R134A" refrigerant gas is disclosed in U.S. Pat. No. 5,015,161, which is assigned to the assignee of the present invention. The '161 patent describes a refrigerant gas compressor having high overall operating efficiency with minimal internal leakage notwithstanding the presence of higher compression levels. The compressor of the '161 patent comprises a two stage rotary ring piston which reduces the pressure differential across the rotary mechanism thereby reducing sealing problems. The rotary piston in the structure of the '161 patent is an orbiting piston which cooperates with a compression chamber and an internal cylindrical post to define two first stage compression chambers and two second stage pressure chambers. The output of the first stage supplies the inlet of the second stage. The orbiting ring piston, which is located between the cylindrical post and the housing wall, rotates about an axis that is offset from the axis of the post as the outer surface of the orbiting ring piston contacts the inner surface of the housing and the inner surface of the orbiting ring piston contacts the outer surface of the post.
External vanes slidably mounted in the housing engage the outer surface of the orbiting ring piston to define two discrete first stage compression chambers. The inner vanes are slidably mounted on the post as they engage the inner surface of the orbiting ring piston, thus defining two discrete second stage compression chambers. The two compression chambers of the second stage are divided and are dynamically sealed, one with respect to the other, at the tangent contact points between the outer surface of the cylindrical post and the inner surface of the orbiting ring piston. Similarly, the compression chambers of the first stage are divided and are dynamically sealed, one with respect to the other, at the rotating points of tangential contact between the outer surface of the orbiting ring piston and the inner surface of the housing.
Refrigerant gas discharged from the first stage is directed through inlet ports to the second stage. Gas discharged from the second stage passes through the compressor outlet to the evaporator and condenser in the air conditioning system.
The positions of the vanes and the respective compression chambers change in relation to the inlet ports in accordance with the variable position of the orbiting ring piston. The vanes are adapted to open and close inlet ports as they move in a generally radial direction relative to the axis of the orbiting ring piston.